Composite Membrane and Method for Manufacturing Such a Membrane

Abstract

The present invention relates to a composite membrane (10) comprising a fibrous fabric (1) of nanofibres (11), wherein the thickness of the fabric (1) is between 10 nm and 50 μm and said fabric is impregnated with a wetting liquid (A). According to the invention, the composite membrane is immersed in a second fluid (B) which is immiscible with the wetting liquid (A), forming an A/B interface between the wetting liquid (A) and the immiscible fluid (B), and the composite membrane is capable of remaining tensioned when it is compressed from its resting state until reaching dimensions corresponding to 5% of its dimensions in the resting state, and when it is stretched from its compressed state until reaching dimensions corresponding to 2000% of the length in the compressed state. The present invention also relates to a process for manufacturing such a membrane.

1 . A composite membrane comprising a fibrous fabric of nanofibers, the thickness of the fabric being between 10 nm and 50 μm, said fabric being impregnated with a wetting liquid, said composite membrane being characterized:
 in that it is immersed in a second fluid which is immiscible with the wetting liquid, forming an A/B interface between the wetting liquid and said immiscible fluid, and 
 in that it is capable of remaining tensioned:
 when it is compressed from its resting state, until reaching dimensions corresponding to 5% of its dimensions in the resting state, and 
 when it is stretched from its compressed state until reaching dimensions corresponding to 2000% of the length of the compressed state. 
 
 
     
     
         2 . The composite membrane as claimed in  claim 1 , wherein the thickness of said fibrous fabric is between 500 nm and 30 μm, and preferably between 1 μm and 5 μm. 
     
     
         3 . The composite membrane as claimed in  claim 2 , wherein said nanofibers of the fibrous fabric have a diameter of between 100 nm and 500 nm, and preferably of about 200 nm. 
     
     
         4 . The hybrid membrane as claimed in  claim 1 , wherein said A/B interface is an oil/air interface, an oil/water interface, or a glycerol/air interface, or an interface of water with surfactant/air. 
     
     
         5 . The use of the membrane as defined in  claim 1 , as an organ capable of developing a mechanical force in reaction to an exterior stimulus, typically an artificial muscle. 
     
     
         6 . The use of the membrane as defined in  claim 1 , for constituting a stretchable electronic circuit. 
     
     
         7 . The use of the membrane as defined in  claim 1 , as a smart power circuit. 
     
     
         8 . The use of the membrane as defined in  claim 1 , as a SLIPS membrane. 
     
     
         9 . A process for manufacturing a composite membrane as defined in  claim 1 , comprising the following steps:
 A. forming a solution, in a solvent medium, of a material capable of being dissolved by said solvent medium;   B. injecting said solution at a flow rate Q into a capillary tube having a diameter do subjected to an electrical voltage U of between 1 kV and 100 kV, the diameter do being between 0.5 mm and 2 mm, and preferably about 1 mm;   C. forming, at the outlet of said capillary tube, a drop of said solution, said drop being electrically charged so as to bring about its destabilization in the form of a cone;   D. ejecting, from said cone, a liquid cylinder toward an electrically conductive target, which is electrically earthed;   E. evaporating said solvent during the ejecting of said liquid cylinder, resulting in a vortex instability generating solid nanofibers of the material;   F. collecting, on a face of said target oriented toward said cylinder, said solid nanofibers so as to form a mat of nanofibers forming a fibrous fabric, said target being, prior to step B, covered with a non-stick coating;   said process being characterized in that it also comprises, at the end of step F, an additional step G of wetting said fibrous fabric with a wetting liquid so as to form a wetted membrane, and   in that it comprises a step H of immersing the wetted membrane thus obtained in a fluid which is immiscible with the wetting liquid, so as to create an A/B interface between the wetting liquid and said immiscible fluid and thus to form the composite membrane as claimed in the invention.   
     
     
         10 . The process as claimed in  claim 9 , wherein said non-stick coating is a parchment paper. 
     
     
         11 . The process as claimed in  claim 9 , wherein:
 said face of the target is a flat face located at a distance L from the outlet of said capillary tube which is between 5 cm and 15 cm, and   said capillary tube is subjected to an electrical voltage U of between 10 kV and 15 kV.   
     
     
         12 . The process as claimed in  claim 11 , wherein:
 said flat surface of the target is located at a distance L from the outlet of said capillary tube which is about 10 cm, and   said capillary tube is subjected to an electrical voltage U of about 12 kV.   
     
     
         13 . The process as claimed in  claim 9 , wherein said constituent material of the fabric is a polymer material chosen from the group consisting of the following polymers:
 polyacrylonitrile (PAN),   polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP),   polyvinylpyrrolidone (PVP),   polyvinyl alcohol (PVA),   polyethylene oxide (PEO), and   polyvinylidene fluoride (PVDF).   
     
     
         14 . The process as claimed in  claim 9 , wherein said constituent material of the fabric is a polymer-inorganic network hybrid material, wherein the inorganic network may be, for example, SiO 2  (silica), TiO 2  (titanium dioxide), Fe 2 O 3 (iron oxide), in the form of an amorphous network or of crystallized nanoparticles. 
     
     
         15 . The process as claimed in  claim 9 , wherein said A/B interface is an oil/air interface, an oil/water interface, or a glycerol/air interface, or an interface of water with surfactant/air.